This invention relates to membrane switches, and more particularly, relates to custom prototype switch panels, kits, and methods for constructing such panels.
Membrane switches are often utilized due to their characteristic reliability and durability, low cost, superior resistance to deleterious environments, and the wide flexibility afforded the switch designer in tailoring a switch design to a particular application.
In order to capitalize on the flexibility afforded by membrane switches, it is frequently desirable to try a number of different switch designs, necessitating construction of a number of custom prototype switches. However, although the aforesaid cost savings may ultimately be obtained in large production runs, one serious problem with a decision to employ such switches is that initial cost for design and construction of a custom prototype membrane switch panel may be quite high, due to the time-consuming and costly steps required, including custom artwork, silk screening processes and the like. While these costs may in some instances even be prohibitive in the case of construction of one such prototype design, the problem is compounded all the more in the aforementioned case wherein numerous prototype designs are desired for testing, such that a designer is frequently precluded from availing himself of the outstanding benefit of flexibility of design uniquely associated with membrane switches.
Attempts have been made in the past to reduce the costs and time-consuming steps associated with production of custom prototype membrane switches. One such typical approach, disclosed in U.S. Pat. No. 4,303,811 to Parkinson, provides to the switch designer a kit containing materials required to produce a custom switch panel. More particularly, a plurality of pre-manufactured switch units, each with a varying number of membrane switches, is provided, and a transparent overlay. The switch unit or units having the desired number of switches is selected (or, if necessary, one is cut down in order to contain the required number). The overlay sheet is then placed over the resultant selection of switches which may then have affixed thereto custom graphic indicia adjacent the respective switches, resulting in a "custom" membrane switch panel prototype.
Numerous design constraints to such approaches have continued to plague the designer. One of the most serious is that while flexibility may have been afforded in the number and layout of switches in the panel, the designer is still limited to the switches and electrical interconnections provided in the switch units themselves, which have been pre-manufactured and preselected for inclusion in the kit.
Moreover, the problem still remains for the manufacturer of the switches and switching units to construct efficiently and provide to the designer a plurality of differing switching and circuit configurations for his use which, as previously noted, can become quite expensive due to the numerous layout and screening process steps and the like.
One such problem in making switch elements and other conductive paths for inclusion in the membrane switch is that of insuring proper registery between the apertures in the insulative spacer separating the upper and lower membranes, and the conductive elements carried on either side of the spacer between the membranes.
Various techniques are employed in layout of artwork for the layers in a membrane switch to attempt to provide registry therebetween, such as use of transparent artwork layouts, layouts having coordinate grids, and registration pins. In the latter case, for illustration, a plurality of stable verticle registration pins may be provided mounted, e.g., in a layout board, and each layer of artwork is provided with mating holes in the edge thereof. In this manner, as successive layers of layout artwork are overlaid in the holes brought into mating registry with the pins, vertical registry will hopefully be maintained in the artwork with respect to any of the layers.
Whereas this approach may be attempted for maintaining registry in large commercial or production runs of switch panels, it will be noted that the artwork thus generated and registered is only an intermediate step, and must be utilized (often in further photographic reduction processes, or the like) in production of final layers which will comprise the membrane switch by techniques known in the art such as silk screening, printing methods, various methods for production of printed circuit boards, or the like. Thus, the occasional designer of custom prototype switches, particularly in the case wherein elaborate layout facilities such as those of membrane switch manufacturers are not available, is still faced with the problem of producing both quickly and inexpensively a very limited quantity of custom design prototype membrane switches which are nevertheless comparable with those commercially available from manufacturers in terms of accuracy of registration, reliability, and the like.
Yet another problem faced by the custom membrane switch designers is that even if they are somehow efficiently able to maintain registration tolerances offered by commercial switch manufacturers, providing custom conductive parts or elements on a limited prototype or non-production basis in a membrane switch can be extremely time consuming when conventional techniques are employed.
As but one example, it is frequently necessary to provide for such conductive paths between the spacer and a membrane. Conventional methods include the etching of conductive traces on the face of printed circuit boards which serve as the switch membranes. However, this necessitates photographic and other steps in order to produce the desired circuit path configurations. Methods and apparatus were thus highly desirable for providing custom conductive paths for use between the spacers and membranes wherein the conventional numerous steps required to produce such paths were substantially reduced, including steps required to provide insulation between conductive paths which cross one another.
These disadvantages of the prior art, including those of the aforementioned U.S. Patent, are overcome with the present invention, and commercially acceptable embodiments of a custom prototype membrane switch panel, kit, and method for construction of same are herein provided which are fully capable of not only providing improved registration between the various layers in a custom prototype membrane switch, but further provide for total design flexibility with respect to the conductive paths provided between each outer membrane and the insulative separator layer disposed therebetween.